Sun glare and visual aberrations or blind spots have been a concern for air safety as long as the aviation industry has existed. Efforts to eliminate or materially reduce adverse effects of the sun have been at best only partially successful.
Sun visors and sun glasses are, of course, the most practical way to reduce or eliminate visual problems caused by sunlight. However, as much as it is desirable to reduce sun glare, it is even more important that vision not be obstructed. Sun visors and sun glasses are effective in reducing the amount of sun, by reducing natural incident light to a third or less of the light which enters the windshield of the aircraft. For that reason, sun visors and sunglasses have been used to reduce the effects of sunlight on the pilot.
However, sun visors and sunglasses have not been successful in reducing blind spots or temporary visual aberrations caused by looking directly into the sun, such as occurs when the aircraft is being flown "up sun" or in the general direction of the sun. This temporary blind spot or visual aberration lasts for from mere seconds to several minutes, depending upon the intensity of the sun and the effectiveness of first order sun visors or sunglasses which are being used by the pilot. Since this often times happens during the busy time, during landing or takeoff, when the direction of flight is governed much more by wind direction and runway layout than it is by the location of the sun in the sky, even short moments of loss of full vision can be extremely dangerous.
Efforts to block the light of the sun so that it does not directly shine on the pilot's eyes have not met with any significant success. Since the sun is the brightest object which a pilot will encounter, total obstruction of the sun's rays by visors would dangerously reduce the field of view of the pilot. Danger during landing and taking off, as well as the risk of mid-air collisions, would be far greater than the danger caused by momentary blind spots or visual aberrations from the sun. Thus, the solution would be worse than the problem.
Depending on position relative to the horizon, the luminous disk of the sun is between 750 and 200,000 times as bright as the sky. A luminous contrast this high means that any total-area light filtration which makes viewing the sun possible will completely obscure the sky and all object viewed against the sky. If, on the other hand, a total-area filter is light enough to permit the viewing of objects against the sky, the sun is blindingly bright. Thus, the only solution is to modulate only the sun (plus its immediate area) to a tolerable level of brightness while leaving the rest of the sky bright enough for clear viewing. That is, what is needed is a light-adjustable eclipse of the sun as viewed by the pilot or other operator.
Accordingly, it is an object of the present invention to provide a device which is useful for restricting or eliminating the danger of a pilot having to view the sun directly.
Another object of this invention is to provide a device suitable for eliminating or reducing the danger from direct sunlight without restricting the field of vision of the pilot. Other objects will appear hereinafter.